The volume of 400 mL of chlorine gas at 400 mm Hg is decreased to 200 mL at constant temperature. What is the new gas pressure?
 400 mm Hg
 650 mm Hg
 300 mm Hg
 800 mm Hg
 18.
 The collision of gas molecules with the walls of its container produces ____________.
 temperature
 density
 volume
 pressure